As provided for by government regulatory agencies, such as the United States Department of Agriculture (USDA), lumber, logs, fruits, vegetables, and other perishable agricultural commodities or products that are imported into or exported out of the regulated territory are mandatorily quarantined and treated, at their point of entry or exit, according to specific protocols and treatment schedules set by the one or more regulatory agencies. This treatment occurs to prevent the introduction, movement and infestation of certain agricultural pests and other target organisms into or within the regulated territory. Such pests include insects, mites and ticks, nematodes, snails and slugs, fungi, and various other vermin. To comply with this regulatory requirement, there are a number of treatment processes that are currently known and used in the industry. One category of treatment processes is chemical treatments that include the use of fumigants and aerosols and/or micronized dusts. The term “fumigation,” as defined in the USDA Treatment Manual, is the release and dispersion of a toxic chemical in such a way so as to reach the target organism in a gaseous state.
By way of example, in the United States, nearly every aspect, ranging from the equipment used to the various steps of the fumigation process itself, is carefully inspected and strictly dictated in USDA regulations and guidelines. The fumigation enclosure is inspected to ensure, for example, that it is well-ventilated and has specific aeration capabilities. Furthermore, due to the high toxicity of the fumigants, a fumigation enclosure must be sealed and airtight when in use and, therefore, it is meticulously tested for leaks in and around the enclosure and the operation equipment.
Further, with respect to the USDA, the fumigation process itself is also carefully monitored. For example, the USDA sets forth a specific dosage rate of the fumigant depending upon the temperature of the product and the type of product being treated. There are also certain restrictions on the amount of volume of a product that can be treated in a given fumigation enclosure. And, specific stages of the process (e.g., the period of time during which air circulation blowers or fans are to be turned off to allow the fumigant to effectively settle in order to take an accurate chemical concentration reading), are also set forth by the USDA. During the fumigation process itself, the fumigant concentration level in the air within the fumigation enclosure is monitored to ensure that effective levels of the fumigant are maintained during the appropriate stages of the process and, thereafter, to ensure that the concentration level has fallen to within safe acceptable limits during aeration of the fumigation enclosure at the completion of the process.
Furthermore, the USDA routinely inspects the product itself to ensure and certify its quality at various points in time before, during and after the fumigation process, according to specific regulations. For example, with respect to fruits and vegetables, the USDA will take a sample number of the product and measure the temperature of the samples to determine whether or not the product temperature is within an acceptable temperature range for that particular fruit or vegetable (e.g., approximately 40° F.) according to the individual USDA treatment schedule that is specific to that type of fruit or vegetable. Depending on the particular product, an elevated temperature may indicate that the product is now in a deteriorating condition.
Within the realm of quarantining and fumigating imported and exported commodities that include perishable agricultural products, there are several methods that are well-known to persons of skill in the art and, for example, are specifically defined and approved of by the USDA. These methods include: (1) tarpaulin fumigation, (2) sealed container or open container (with the addition of a tarpaulin) fumigation, and (3) chamber fumigation, using either a normal atmospheric pressure (NAP) chamber or a vacuum chamber. Depending upon the specific circumstances in each case, such as the nature and dimensions of the product, one fumigation method may be more suitable than another. Below is a brief summary, in simple general terms, of each of these three methods. As described in detail below, in each instance, agency regulations typically require that a restrictive perimeter be maintained around the fumigation site for specific periods of time during the fumigation process and that a specific period of time must be allowed for aerating the fumigation enclosure into the open atmosphere before the product may be released at the completion of the fumigation process.
In tarpaulin fumigation, which is a relatively primitive process, a flexible tarp is secured and sealed over and around cargo that has typically been arranged in a square or rectangular shaped stack. To permit air movement along the floor and between the various cargo, the cargo is arranged on pallets or in open containers before being surrounded by the tarp. To seal the tarp around the cargo in order to prevent the fumigant gas from leaking out from under the tarp, sand snakes are oftentimes used to weight down the fringe of the tarp to the floor. The fumigant gas is then administered under the tarp using gas introduction lines and is distributed amongst the cargo using circulation fans having the capacity to move a certain volume (in cubic feet per minute) until a prescribed amount of gas has been administered and distributed inside the tarp. Once the fumigant has taken its full effect, fans are used to aerate the air from beneath the tarp and up into the open atmosphere until a prescribed amount of time has passed and the gas concentration readings indicate that the fumigant concentration level has fallen below a certain regulatory threshold level. Following this active aeration process, the cargo is “passively” aerated by simply removing the tarp and allowing the cargo to air out before it is finally released. Ordinarily, this kind of fumigation process is conducted at ambient temperatures, which can be detrimental to the perishables being treated depending on the climate conditions of the geographical location.
Container fumigation is conducted similarly to tarpaulin fumigation, but instead is conducted inside a container that is typically comprised of an ocean container or a domestic trailer containing palletized cargo. The container is placed in a well-ventilated area and is effectively sealed with either its doors closed, or, the container is left open and is sealed under a tarp. All of the vents of the container are sealed. Thereafter, the fumigant gas is introduced into the container using a gas line that is attached to a rear gasket of the container. The gas is then circulated inside the container using axial-type blade fans that have been installed inside the container. At the completion of the process, the container doors are opened and the circulation fans are turned on to expel the toxic air up into the open atmosphere until a prescribed amount of time has passed and gas concentration readings indicate that the fumigant concentration level has fallen below a certain regulatory threshold level.
In chamber fumigation, the fumigation enclosure is comprised of a specially designed and constructed normal atmospheric pressure (NAP) chamber or a vacuum chamber. Inside the chamber are circulation fans and an exhaust system. Prior to operation, the integrity of the chamber is tested by pressurizing the chamber and, thereafter, the chamber is inspected for any resultant pressure leaks. The chamber pressure is then relieved. Once the chamber is approved for use, cargo is loaded into the chamber. Depending on the type of product and the way in which it was packaged during shipping, pallets are either loaded directly into the chamber or, alternatively, the pallets are left inside their shipping container and the entire shipping container itself is loaded into the chamber such that the pallets and the container are fumigated simultaneously. Once the chamber is sealed, the fumigant is inducted into the chamber. The fumigant gas is circulated inside the chamber for a certain period of time. Using the exhaust system, the chamber is then aerated up into the open atmosphere until gas concentration readings indicate that the fumigant concentration level has fallen below a certain regulatory threshold level. In the case of a vacuum chamber, the vacuum remaining at the end of the fumigation is brought to zero by temporarily opening an air intake valve. The valve is then closed in order to draw a vacuum, and then the vacuum is released again. This process is repeated for as many times as necessary to adequately aerate the chamber.
Irrespective of the particular process that is used, fumigation remains to be a highly effective method for eliminating pests and other undesirable organisms from agricultural products. However, due to the characteristics of the fumigants themselves and the need for a fumigation enclosure, importers, exporters and the agricultural commodity industry at large face a particularly difficult challenge in preserving the fragile nature of perishable goods and handling the toxicity inherently present throughout the fumigation process.
For example, because fumigation requires a sealed enclosure in order to contain the fumigant so that it can reach and maintain an effective concentration that is, unfortunately, extremely toxic and most certainly fatal, the agricultural product must be loaded and unloaded into the sealed enclosure as described above. Also, because the fumigant is a gas, it must be evenly distributed and well-dispersed amongst the units of the agricultural product to be effective. Yet, in some cases, depending on the type of agricultural product, the products are transported and kept in certain packaging to protect them from being physically damaged (e.g. squeezed or crushed), or to limit their exposure to light and heat that may induce premature spoiling of the product. However, if the packaging is not readily permeable by the fumigant, as is the case with certain plastic wrappings that include cellophane, films, shrink wrap, and waxed, laminated, or waterproofed papers, the packaging must be perforated, removed, or opened before fumigation. Therefore, to ensure the maximum effectiveness of the fumigation, products are often unduly handled and/or exposed, which may harm the quality and appearance of the product.
In another example, the USDA has indicated that less fumigant is required when fumigating at higher temperatures thereby suggesting that fumigants are most effective when used at certain temperatures. Therefore, in treatment schedules, for example, that are specific to each type of agricultural product, the USDA prescribes a lowermost temperature point or range for the product temperature while inside the fumigation enclosure. For example, with respect to certain grape varieties, the individual USDA treatment schedule for that product provides that its product temperature cannot fall below 40° F. This lowermost temperature point of 40° F. is common to a relative majority of agricultural products. Thus, in logical terms, with the exception of cold climate areas during their cool season(s), most, if not all existing fumigation processes are conducted at ambient temperatures. However, many perishable agricultural products are intentionally stored, shipped, and/or transported in refrigeration, which is generally below 40° F., to extend their shelf life by either preserving the product at its peak ripeness or by delaying or stunting its ripening stage. The advent of refrigeration revolutionized the agricultural commodity industry by making it possible to have a perishable product that is not locally grown (or produced), nonetheless, reach an end consumer in its best condition, which is essential to the success of any product. Yet, in order to be fumigated in temperatures at or above, for example, 40° F., as is dictated by, for example, USDA treatment schedules, these products must be brought out of refrigeration and, as a result, are exposed to variable temperature conditions that can cause premature spoiling and adversely affect the quality, nature, and shelf life of the product. Even in the case of cold climate areas where the ambient temperatures are cool enough at certain times of the year to obviate the need for refrigerating the product, the product may need to be brought out of the ambient air temperature in order for the fumigant to be effective. Thus, in nearly every instance of ambient temperature fumigation, regardless of climate, the product will experience some type of uncontrolled temperature drop and/or spike during the fumigation process. As can be appreciated by those skilled in the art, exposure to swinging variations in temperature are detrimental to the quality of the product and, in some cases, will interrupt or upset the ripening stage of the product or cause the product to prematurely spoil.
In a further example, the harsh toxicity of the fumigants adversely affects the quality of the product and threatens the health and safety of the fumigators and the surrounding environment. Unfortunately, toxic concentrations of the fumigant settle on the treated product during fumigation and, during aeration of the fumigation enclosure, the residual fumigant gas is released into the open atmosphere where it settles on work surfaces and on the ground outside the fumigation site. Although fumigants are known to be highly toxic and exposure to certain fumigants is known to harm the shelf life of fresh fruits and vegetables, as well as the viability of dormant and actively growing plants and the germination of seeds, the USDA, in its Treatment Manual, states that the adverse affect “is a necessary risk in order to control pests.” Therefore, the USDA, for example, requires that the fumigation site be located in an area that is isolated and can be secured to prohibit and/or restrict traffic and people from entering within a certain perimeter surrounding the site. Thus, while the USDA requires that there be a particular surrounding perimeter of, for example, 200 feet, in which access to the site is limited or forbidden (especially in areas downwind of the exhaust duct), there currently are no requirements that the fumigants be substantially filtered or removed from the exhaust air before it is expelled into the atmosphere. Therefore, given the choice, many fumigation operators do not take any steps to clean the exhaust air in order to forgo the additional high costs associated with the cleanup. To aerate the fumigation enclosure, operators simply remove the tarp, open the container or chamber doors, or force the exhaust through a duct and into the atmosphere by running their exhaust systems. Without taking any steps to actively remove the fumigant from the exhaust, the air circulation or exhaust system is relied upon to aerate the fumigation enclosure and bring the concentration of toxic gas inside the fumigation enclosure to within acceptable levels. Accordingly, this process takes a significant amount of time to complete (approximately 4 hours) and, to minimize the risk of harmful exposure to persons nearby the fumigation site, aeration must typically wait until activity around the fumigation site is at its least. As a result, the number of fumigation cycles that can be carried out during the course of a day is limited.
Accordingly, a need exists to overcome the problems discussed above.